Development of a novel microfluidic device: a tool for screening combination therapies

A novel diffusion-based microfluidic gradient generator relying on passive diffusion was optimized. Fluorescent dyes were utilized in order to characterize the orthogonal concentration gradients across a chamber reserved for cell cultures. Prior studies suggested that optimized gradients could be obtained by treating the microfluidic device with tetraethyl orthosilicate (TEOS). In this work, several flow experiments were performed and the usage of various fluorescent dyes has shown that dyes with a large molecular weight tend to diffuse relatively slowly, and as a consequence disrupt greatly the establishment of the required orthogonal concentration gradients. This problem arised in TEOS-treated as well as in non-treated devices. Nevertheless, results demonstrated that dyes with lower molecular weight provided a stable linear concentration gradient lasting several hours. Finally, immunocytochemistry was performed on biological cells that were seeded in the treated devices in order to assess whether there were any possible toxic effects from the silicate. Interestingly, no apparent toxicity was observed, suggesting that further experiments involving the application of orthogonal gradients of drugs or inhibitors on cells could be performed with TEOS-treated devices. The biochemical interactions could be thus investigated, bringing this technology a step closer to becoming a potential and highly valuable tool for rapid, cost-effective and high-throughput screening of drug compounds. Microfluidics can help pharmaceutical companies to not only minimize the colossal costs generated during drug discovery and development, but also increase the chances of finding novel and potent drugs.